1. Field of the Invention
This invention relates to agricultural implements and, more particularly, to a holder for a soil working tool that is selectively adjustable in a vertical direction relative to a support therefor.
2. Background Art
It is known to mount soil working tools on a support so that the tools are selectively adjustable vertically relative to the support. A wide range of soil working tools are mounted in this fashion, among which are fertilizer/additive applicators, opening and closing wheels, residue resituating wheels, etc. These tools may be adjusted individually or in groups as dictated by the particular procedure, the terrain, the soil type, etc.
Typically, the holder is in the form of an elongate shaft, which may be straight or contoured. The bottom of the shaft is configured to carry one or a plurality of tools. The top of the shaft has a straight portion which is used to maintain the tool holder on the support.
Typically, the straight shaft portion is held captively between a pair of plates on the support. The plates are contoured so that they cooperatively define a receptacle to receive the straight shaft portion and allow the straight shaft portion to be guided vertically relative to the support plates.
A plurality of nuts and bolts are used to draw the plates towards each other. By tightening the bolts, the straight shaft portion is squeezed between the plates so that its vertical position is fixed. By loosening the nuts, the plates can be moved away from each other so that the straight shaft portion is allowed to slide vertically in guided fashion relative to the plates.
In its simplest state, the straight portion of the shaft, including the upper free end thereof, has a uniform cross section. By slightly loosening the bolts on the plates, the shaft free end can be directed upwardly from beneath the plates into the receptacle. When a desired heights for the holder is realized, the bolts on the plates are tightened to captively maintain the holder in a fixed position between the plates.
While this construction facilitates assembly of the holder, it introduces an element of danger. If the nuts on the plates are loosened, the holder with the tool(s) thereon can slide freely downwardly and separate from the support. Since the combined weight of the holder and tools may be significant, bodily injury may result from an inadvertent movement of the holder with the tools thereon. This is particularly a problem in the agricultural environment in which corrosion and foreign matter, such as soil and chemicals, may build up within the receptacle defined by the plates. The corrosion and foreign matter may cause the straight shaft portion to stick in the receptacle. As the user progressively loosens the nuts on the plates, the shaft may abruptly and unexpectedly break loose and fall.
To overcome the above problem, it is known to drill a through bore at the top of the holder to accept a deformable key or pin. Since the pin and key are relatively long, it may be impractical to pre-assemble the pin/key before mounting the holder. Consequently, the user typically directs the holder upwardly into the receptacle defined by the plates until the through bore is exposed at the top of the plates. The user then inserts the pin/key, and in the latter case effects the necessary shaping of the key to hold the key in place.
It is inconvenient to have to assemble the pin/key. If this procedure is performed by one person, the user risks dropping the holder and facing the aforementioned dangers. The pin/key also defines a sharp projection which could injure the user.
A still further problem associated with the pin/key is that the pin/key must have a relatively small diameter so that the accommodating bore will not significantly weaken the shaft. Consequently, the pin/key is prone to shearing as the holder slides downwardly relative to the plates. Aside from the possible danger resulting when the pin/key shears, the shaft may have to be re-bored to remove the remaining pin/key fragment.
Another problem with conventional holders is that it is difficult to consistently set a desired height therefor. It is known to place graduations on the straight shaft portion to provide a frame of reference between the plates and holder. The graduations may be painted on, or defined by bores, as may be provided in a hollow shaft.
The problem with the conventional graduations is that they often become obscured as a result of the severe conditions under which the equipment is operated. The painted graduations may be worn off the shaft as the shaft moves guidingly against the plates. Bores or any depressions in the shaft tend to rapidly fill with dirt, fertilizer, additives, etc. so as to eventually become undetectable.
In the absence of any graduations, or in the event that the graduations become ineffective, the user is required to manually measure the height of each holder. This is a time consuming endeavor and, depending upon the nature of the holder, may be awkward and dangerous. If a single individual attempts to effect the adjustment, he/she must raise the holder, use a tape measure to select the height, maintain that height and tighten the nuts on the plate bolts to fix the position of the holder relative to the plates.
It is also common to limit rotation of the holder about its vertical axis within a predetermined range. This is commonly accomplished by welding a vertically extending rib onto the shaft so that the rib makes keyed connection with the plates to limit rotation of the holder about a vertical axis. The need for the rib introduces another manufacturing step for the holder, which undesirably adds to its costs.